If there are a longer series of related commits, consider a merge instead:

git fetch upstream-rwgit merge --no-ff upstream-rw/master

The merge will be detected by github, and should close any related pull requests
automatically.

Note the --no-ff above. This forces git to make a merge commit, rather than
doing a fast-forward, so that these set of commits branch off trunk then rejoin
the main history with a merge, rather than appearing to have been made directly
on top of trunk.

Now, in either case, you should check that the history is sensible and you have
the right commits:

git log --oneline --graphgit log -p upstream-rw/master..

The first line above just shows the history in a compact way, with a text
representation of the history graph. The second line shows the log of commits
excluding those that can be reached from trunk (upstream-rw/master), and
including those that can be reached from current HEAD (implied with the ..
at the end). So, it shows the commits unique to this branch compared to trunk.
The -p option shows the diff for these commits in patch form.